Exceptional Events

Exceptional events have become a significant air quality policy and technical challenge facing state, Tribal and local air agencies. Increasing wildfire and prescribed fire activity, windblown dust, stratospheric ozone intrusions, and other natural events influence monitored concentrations of ozone and particulate matter, affecting regulatory determinations under the Clean Air Act. The purpose of the exceptional events rule is to ensure that regulatory decisions under the Clean Air Act are not biased by monitored air quality data over which a state has little or no control.

WESTAR-WRAP serves as a regional forum for agencies to coordinate and share information regarding exceptional event demonstrations. WESTAR-WRAP coordinates national workshops, training, development of tools, and facilitates ongoing discussions among agencies working on exceptional event demonstrations.

WESTAR-WRAP is coordinating an effort lead by staff at the South Coast Air Quality Management District (SCAQMD) to develop an online app to assist air agencies in preparing an Exceptional Events (EE) Demonstration for submission to the EPA. This interactive app lays the ground work for automating much of the technical data collection required in Exceptional Event Demonstrations. The online tool is a collaborative project among air quality regulatory agencies across the Nation. It is, and will continue to be, a work in progress. If you are interested in contributing to this project, please contact Rhonda Payne at WESTAR or Jay Baker at WESTAR.

• April 2025 EE app training recording.
• A demonstration of the app from a MARAMA webinar can be viewed here.

While use of this app in no way guarantees EPA concurrence for any EE demo submitted to the EPA, we are working with them to make sure the outputs meet the requirements of the EE rule. EE demos created using this app will be subject to the same review process as EE demos that do not use this app.

EPA’s Exceptional Events Analysis and Visualization Tools

• Informational Webinar on EPA’s New Exceptional Events Implementation Tools – Recording and Slides
• Tools to assist in data screening and determining regulatory significance can be found on EPA’s website and the tiering tool is here:
  • PM2.5 Wildland Fire Exceptional Events Tiering Document
  • PM2.5 Tiering Tool for Exceptional Event Analysis

EPA September 2016 Final Rule and Guidance

• EPA’s Exceptional Events Rule and Guidance

Historically, WRAP’s exceptional events activities were coordinated through the Fire and Smoke Work Group’s Exceptional Events Support Team. Meeting materials from that effort are included below. Going forward, WESTAR-WRAP will support exceptional event coordination across a broader range of technical and policy topics, and all material will be posted here.

Thank you to all those who helped organize, present, host, and attend the National Exceptional Events Workshop. All of the meeting presentations and recordings are posted here for you to review and learn.